Flanged tubes, such as those used in tri-clamps, and similar to the novel one shown generally in FIG. 7, include four basic components (such as tri-clamp couplings constructed according to ISO 2852, DIN 32676, BS 4825). A pair of tubes 110 having flanged ends configured to register against one another and to enclose a sealing gasket 115 to create an airtight and fluid-tight seal. The flanges are maintained in registration with a clamp structure 130 commonly comprising a pair of hinged semi-circular, or 3-segment, clamping segments with corresponding locking structures at ends opposite a hinged end. The locking structures may include a threaded bolt and threaded bore in one clamping segment and corresponding registration surfaces in the second clamping segment. The flanges may have radially sloped surfaces on a side of the flanges opposite the surfaces that register against one another when two tubes are aligned. The slopes decrease away from the tube body from which the flanges extend. When the clamp structure is secured to the mated flanges, tightening the clamp structure against the paired flanges pulls the semi-circular clamping segments against the sloped surfaces of the flanges. Increased tightening increases the axial and radial pressures exerted against the flanges that cause the flanges to be pressed together in an axial direction as well as a radial direction. The more the semi-circular segments are torqued together, the more tightly the flanged tubes are secured together.
Tri-clamp tubes and their associated flanges are often fabricated from metals, such as 316L stainless steel, and used in sanitary piping and filtration systems. Those metal based tri-clamp coupling systems are often used repeatedly and can sustain various high temperature and high pressure applications and processes. Polymer materials (e.g., polypropylene, polysulfone. PVDF, etc) used for polymer-based tri-clamp tubes and associated flanges are becoming necessary and popular in single-use disposable piping, filter capsules and bio-containers used in manufacturing and processing applications in the bio-pharmaceutical, medical, and food and beverage industries. The polymer materials used for these structures offer many advantages including ease of manufacture, good structural integrity, durability and lowered susceptibility to bacterial growth. There are, however, drawbacks to use of polymeric materials when the application to which the tri-clamp construction is used requires regular and periodic sterilization procedures such as those used in the pharmaceutical industry.
Chief among the drawbacks is the propensity of some of the polymer-based flanges to deform during prolonged autoclaving and other high temperature sterilization techniques. This is due at least in part to the thermoplastic nature of the polymer materials commonly used. Even though the sterilization procedures may be performed with the tri-clamp apparatus in a clamped condition, the flanged portions of the tri-clamp coupling assembly can deform when heated and cooled cyclically. The deformation can lead to improper sealing between mated flanges as well as a reduction in structural integrity after the sterilization procedure. What is needed is a disposable tri-clamp tube flange that can withstand repeated and prolonged high-temperature sterilization procedures without any degradation of structural integrity, flange strength or ability to maintain an airtight and fluid-tight seal.
One approach to correct this problem is to incorporate a metallic insert into the end of a tube to function as the flange portion secured in a tri-clamp. As shown in FIGS. 1-3, a tube insert, shown designated generally as 10, includes a generally cylindrical body 12 with a radially extended annular flange 18. Flange 18 includes an annular rim 20 that forms the perimeter surface to which the clamping arms of a tri-clamp register against. A tapered surface 19 of flange 18 slopes radially outwardly from body 12 with the taper becoming thinner toward the outer perimeter of flange 18. This configuration provides a means to impart an axial force on the flange as it registers against a mated flange of a second tube. As the clamp is tightened, the clamping arms impart a radially inwardly directed force against flange rims 20. As portions of the clamping arms in registration with sloped surfaces 19 are further tightened, the clamping arms slide along the sloped surfaces and impart an axial force that pushes the mated flanges in opposing axial directions to press the mated flanges against each other.
To secure this type of flange insert to the tube, a series of features are needed to secure and seal the metallic insert to the polymeric tube. As the materials used to make the metallic insert and the polymer-based tube differ and do not adhere to each other, mechanical interlocking means are necessary to secure the components together.
A cylindrical transition body segment 14 is formed between, and connects, flange 18 and body 12. At the juncture of the flange 18 and segment 14, an annular shoulder 16 is formed to act as a stop and registration surface when flange 18 is put in a mold used to form tube 32. An annular locking channel 28 is formed on an outer surface of body 12 proximal to shoulder 16. When polymer material is poured or injected into a mold used to form tube 32, the material flows into channel 28 and forms an insert restriction ring 34, integral to tube body 12 that substantially prevents axial movement of flange 18 relative to tube 32. A second annular seal channel 30 is formed toward a distal end of flange 18 to receive an O-ring 36. O-ring 36 is placed in channel 30 prior to the placement of flange 18 in the tube mold. Once the tube material is poured and cured, O-ring 36 ensures an airtight seal is maintained between an inner wall of tube 32 and an outer wall of flange body 12. The presence of the O-ring is of particular importance in this configuration as the materials used for the flange and the tube expand and contract at different rates and to different extents when cycled through periods of heating and cooling such as would be expected in a heat-based sterilization procedure. The presence of the O-ring ensures a substantially air-tight seal is maintained between the registered surfaces when undergoing cycles of heating and cooling.
This configuration does address problems with flange deformation and seal failure, but presents an additional set of issues that make the solution less than desirable. The first issue is the exposure of the metallic flange to the fluids and/or gases introduced into the tube/flange assembly when assembled to a second tube secured with the tri-clamp. Due to this exposure, the materials used for the flange may have to be selected so as not to react with the fluids and/or gases. This potentially limits the selection of materials that could be used to construct the metallic flange. As the flange material differs from the tube material, fluids and/or gases that may be compatible with the tube polymer material may not be suitable for exposure to the metallic material thereby limiting the range of fluids and/or gases that may be used in the apparatus having the tri-clamp.
A second problem is the need for tight dimensional tolerances between the tube and flange segment to achieve a commercially acceptable seal between the parts that must be maintained through cycles of use, cleaning and sterilization. The relatively complicated construction also adds considerably to the cost of producing the flange.
Another approach taken to solve the flange failure issue is to incorporate a cylindrical support into the end of the tube, such as shown in FIGS. 4-6. A modified tube/flange/insert assembly shown designated generally as 50 includes a cylindrical tube body 52 with a radially extending annular flange 54. A metallic cylindrical insert 56 is secured in the end of tube 52 so as to be slightly below the surface defined by a top annular surface 62 of flange 54. A tri-clamp gasket channel 58 combines with a gasket seal face 60 to provide a surface against which a tri-clamp gasket can seal.
The inner diameter of insert 56 is dimensioned to be substantially equal with the inner diameter of tube 52. This ensures a smooth transition from the tube body to the insert so as not to impede fluid and/or gas flow through the tube. Although this configuration provides additional support for the flanged tube end, the material comprising the annular flange outside the diameter of the insert does not benefit from the insert's support. The radially distant flange portions are subject to the same issues regarding flange deformation and potential leakage.
What is needed is a simplified flange insert that eliminates the need for accessory sealing means, e.g., O-rings, to ensure a proper, substantially airtight seal between the insert and the tube material. What is needed also is an insert that can be implemented in a manner to prevent any contact with fluids and/or gases flowed through the tubes and tri-clamp apparatus, or any similar apparatus such as a flanged filter housing. What is needed further is a means to secure a flange insert to accommodate expansion and contraction events due to heat-based sterilization procedures without compromising the seal between mated tube flanges and without any substantial reduction in the structural integrity provided by the insert. These and other objects of the disclosure will become apparent from a reading of the following summary and detailed description of the disclosure.